With fast development of wireless communications technologies, a larger network capacity is required. However, spectrum resources in conventional wireless communication frequency bands are increasingly insufficient, and cannot satisfy a future requirement for high-speed wireless communications. Therefore, frequency bands above 6 gigahertz (GHz) attract the industry and the academia. There are sufficient spectrum resources on frequency bands above 6 GHz, which can support wireless transmission at gigabits per second (Gbps) in approximately 200 meters. However, during electromagnetic transmission, a space loss is inversely proportional to a wavelength. A higher transmission frequency indicates a shorter wavelength and a larger space loss. Therefore, a space loss generated in wireless transmission using a high frequency band is greater than a space loss in wireless transmission using a low frequency band.
At present, to reduce a transmission loss of a high-frequency spatial channel and increase a coverage area of a base station, a large-scale antenna array is mainly used for high-frequency wireless communications to form a high-gain narrow beam for transmission. In this way, path and reflection losses and the like that are generated due to large channel space during high frequency transmission are offset. Specifically, a larger-dimension antenna array indicates a narrower beam formed and a larger antenna gain. A base station (Base Station, BS for short) and a mobile station (Mobile Station, MS for short) establish a wireless communication link by means of beam pairing. An antenna array on the BS side sends a beam, and an antenna array on the MS side receives a beam. Sweeping is performed on beam directions of both the BS side and the MS side, to find an optimum beam pair and implement beam pairing between the BS side and the MS side. In this way, an optimum communication link is established between the BS side and the MS side.
However, at present, when a large-scale antenna array is used for high-frequency wireless communications to form a high-gain narrow beam for transmission, beam sweeping needs to be performed on both the BS side and the MS side. For example, a dimension of an antenna array on the BS side is 16×16, a beamwidth is approximately 6 degrees (deg), and 60 beams need to be swept in an area covering 60 degrees (deg) of horizontal space and 50 degrees (deg) of vertical space; a dimension of an antenna array on the MS side is 4×4, and 16 beams need to be swept. To establish an optimum communication link between the BS side and the MS side, sweeping needs to be performed 60×16=960 times on the MS side. If one microsecond (μs) is required in each time of sweeping, one millisecond (ms), that is, approximately one LTE subframe, is required to complete the foregoing beam sweeping. Consequently, using beam sweeping to establish and maintain a communication link consumes a quite large proportion of overheads in a high-frequency wireless communication system.